The present invention relates to a cultured fish feed which is a carotenoid added feed with proanthocyanidin added.
In the fish culture it is well known that the quality of cultured fishes is inferior to that of natural fishes. Taste and smell of food fishes are important, but first of all, food fishes must appeal to consumers. To this end, good color tones of fish bodies and fish meat brilliance are essential.
In view of this, for increasing commodity value of fishes various effective coloring matters have been accumulated in fish meat and body skin. To given a example, carotenoid, such as asthaxanthine, canthaxanthine, etc. has been added to feed for cultured fish. However, a number of factors are involved in good fish body color tones and fish meat brilliance, and it has been a problem that resorting to carotenoid alone affects those of the factors, such as the color of bloody-colored fish meat, etc.
To solve such problem the culture method of simply adding proanthocyanidin to feed has been conventionally developed (refer to, e.g., Specification of Japanese Patent Laid-Open Publication No. 225266/1998).
This prior art has an advantage of increasing kinds of coloring additives to feed, but has a disadvantage that increase of kinds of additives and increase of addition amounts add to the prices of the feed.
In order to solve the disadvantage of the conventional cultured fish feed, the present invention aims to provide a cultured fish feed to which carotenoid is added and polyphenol is further added so as to redouble the effect of fixing carotenoid to fish bodies, whereby addition amounts of carotenoid to the feed can be decreased as much as possible, and the feed is accordingly inexpensive and has the coloring effect superior to that of the conventional feed with the coloring matters added. Furthermore, the present invention aims to suppress occurrence and generation of activated oxygen and peroxide in the fish body, and to thereby prevent obstruction of the growth and metabolism in the fish body. In addition, the present invention aims to reduce defects caused by the oxygen""s effect against the color tone, flavor and brilliance of fish meat. Thus good quality of growing fish body can be improved.
The cultured fish carotenoid added feed according to the present invention contains carotenoid for improving the color tone and meat brilliance of cultured fishes contains a prescribed amount of proanthocyanidin added to a culture fish feed containing a carotenoid group coloring material.
One embodiment of the present invention will be explained below.
First, the cultured fishes the present invention relates to are freshwater fishes, e.g., trouts, such as rainbow trout, carp, colored fishes including goldfish, and seawater fishes, such as sea bream, salmon, tuna, yellow tail, robster, pet fishes, etc.
According to the present invention, coloring of the bodies of fishes, e.g., body color tones, fish meat brilliance, etc. can be redoubled. Here, color tone means lightness and saturation of the surface of a fish body. Fish meat brilliance means lightness and saturation of the meat of the edible part of a fish body.
The cultured fish feed of the present invention comprises a substrate, and additives for improving the substrate. The substrate comprises substrate materials, and substrate additives.
The substrate material is composed of mainly animal feed, e.g., fish powder; cereals; bran; etc. The substrate additives are various vitamin preparations for assisting formation of fish bodies, required inorganic materials, and asthaxanthine (0.004-0.02 wt. % (percent)), which is a carotenoid, as a coloring material. The substrate improving additive is proanthocyanidin (0.004-0.04 wt. % in pellets), which is polyphenol.
Next, a coloring component for coloring fish bodies will be explained.
Asthaxanthine, which is the coloring material as one of the above-described substrate additives, belongs to the carotenoid coloring matter and is abundant in crustacean among acquatic products. It is know that asthaxanthine is an essential coloring factor of sea bream. This material, which is intrinsically very unstable in acidic environment, and tends to decompose, and is, even in neutral or basic environment, easily oxidized (such as air-oxydation), as same as other coloring matters in carotenoid group. When the asthaxantine has such decomposition and deterioration, etc. by acid and due to oxidation, asthaxantine in fish bodies inevitably accordingly decreases. Additionally, such decomposition and deterioration change color tones of the fish meat of fishes. The color change is generally to reddish dark color, i.e., dark reddish brown or purple, which much reduces commodity values of fishes.
According to the present invention, in order to prevent such decrease of asthaxanthine in a fish body and prevent such harmful color tone change of asthaxanthine, a substrate improving additive is added to the substrate. Here, proanthocyanidin is used as the substrate improving additive.
On the other hand, proanthocyanidin used as the substrate improving additive forms the aglycon of anthocyanidin, which is a flavonoid group glycoside coloring material and controls color tones of the coloring material. The color tones change in a wide range from yellow to orange and to red.
Anthocyanidin chemically has trihydroxyphenylbenzopyrilium skelton as the basic structure. Chemically anthocyanidin has basically benzopyrilium structure and stable when acid. When very weak acidic and when basic, anthocyanidin has various quinoid structures, and has various color tones depending on pH""s, and is very unstable when neutral and basic and fades.
The chemical properties of asthaxanthine (the substrate additive) and proanthocyanidin (substrate improving additive) described above are compared with each other as follows.
With reference to this comparison table asthaxanthine and proanthocyanidin will be compared with each other. When acidic, asthaxanthine is chemically very unstable while proanthocyanidin is chemically stable. That is, chemical properties of both coloring materials are complementary with each other when very weak acidic.
On the other hand, fishes are observed. The fish meat of healthy fishes is very weak acidic (pH: about 5-6). When asthaxanthine alone is dispensed, the asthaxathine is broken while passing through the acidic environment when taken in a fish body, and even after taken in good quality, the asthaxanthine is exposed to the state which makes the asthaxanthine unstable in the fish meat. This is a cause for the very low yield of asthaxanthine in a fish body.
The present invention has noted this point. In order to remedially compensate this property of astaxanthin which should be called a weak point, a red-group coloring matter which is stable in acidic environment is added, and is specified by proanthocyanidin, whereby high yields of astaxanthin in a fish body, a small dose of astaxanthin to cultured fishes, and a small addition amount of astaxanthin to the feed are realized.
With the feed with a reduced addition amount of asthaxanthin, fishes are less burdened with carotenoid, whereby the meat of the fishes can be healthy and be made comparable with that of natural fishes.
Furthermore, proanthocyanidin as the above-described substrate improving additive is added, whereby peroxide value and acid value of meat of fishes can be much reduced, whereby taste of the edible parts of the fishes can be long retained. As an additional effect, affection of fishes by deteriorated lipid of the feed can be reduced.
A color improving coloring matter is thus specified as one feed substrate improving additive, and can be added to the substrate of the feed at an arbitrary point of the feed production, so that the addition of the color improving coloring matter can be optionally adjusted in accordance with various conditions, such as supply of raw materials of the feed, etc. The preparation of the feed can be more flexible herein.
According to the cultured fish carotenoid and polyphenol added feed, remarkable advantageous effects that smaller amounts of carotenoid may be added to cultured fish feeds, lightness and saturation of fish bodies and brilliance of fish meat can be improved, and health of fishes is much improved, and other advantageous effects can be produced.